This invention relates to a pipette controller and, more particularly to an improved pipette controller which is formed in a very compact structure so that it can be used easily with one-hand.
Some pipette controlling means are known, such as the one described in U.S. Pat. No 3809297 issued May 7, 1974 to John Poulten Limited, where a helical spring is used for biasing piston upward to a predetermined position in order to draw liquid into the pipette, said helical spring is arranged in a generally cylindrical cover. In order to contain the extended helical spring, this cylindrical cover should have a substantial large volume which is almost the same as that of the cylindrical device which is connected to the cylindrical cover, hence the entire volume of such pipette controller is substantially increased. In addition, the construction of such pipette controlling means is somewhat complicated due the fact that two rods in screw-threaded engagement with each other are used for varying the length of the piston rod. And a spring clip is used for movably closing an aperture in the bottom of the cylinder in order that the aperture can be opened to atmosphere for discharging liquid from the pipette. However, in order to open aperture to atmosphere, the spring clip needs to be pressed downwards by the same hand that holds the pipette controlling means, thus making one-handed operation of the pipette controller difficult.
Accordingly, it is an object of the present invention to overcome the above disadvantages.
It is a further object of this invention to provide a pipette controller that permits convenient operation and excellent control for pipetting with the facilities of the graduate reading device for presetting the volume of liquid to be filled.
It is another object of this invention to provide a compact pipette controller having a coil spring arranged in a cylinder between the bottom of the cylinder and the piston for biasing the piston to a predetermined position which eliminates the need to add complicated and space-consuming parts to contain the coiled spring.
It is another object of this invention to provide a pipette controller utilizing a hand controller for controlling the natural drainage of the liquid by means of a lever action.
It is another object of this invention to provide a pipette controller utilizing a double-sealing means which can sealingly grip the end of the pipette.
According to this invention, the pipette controller comprises a cylinder having, at its tubular extension, a port provided with two seal members and a collet for sealingly gripping the end of a pipette; a cylinder cap mounted on the upper end of the cylinder; a piston capable of reciprocation inside the cylinder; a coil spring arranged in the cylinder between the piston and the bottom of the cylinder for biasing piston to a predetermined position; a threaded rod having one end connected to the piston and the other end connected with a plunger movably projecting through an opening on the top of the cap, said plunger includes radial flange on the lower end thereof to be biased against the inner side of the top of the cap by said coil spring for normally maintaining the upper end of the plunger projected outside the cap, said plunger further includes a hollow tubular member of transparent material, a nut member for threadedly engaging the threaded rod such that the upper end of the thread rod will be caused to ascend or descend with respect to the wall of the tubular member when the plunger is turned, and, a set of graduations is provided on the surface of the wall of the tubular member in cooperation with an indicating means provided on the upper-most end of the threaded rod inside the tubular member to indicate the volume of the liquid being sucked in by the travel of the piston. In a preferred embodiment, the tubular extension of the cylinder is further provided with a second port communicating to atmosphere via a channel; which channel is normally closed by means of an operable lever system attached to the barrier for controlling the natural drainage of the liquid.
This invention will become fully apparent from the detailed description with reference to the accompanying drawings which are given by way of illustration only, and thus are not limitative of this invention.